The filter is the hardest working part of a plug-in hot tub that nobody looks at. It catches skin flakes, hair, sun cream, leaves and grit so they do not end up in the pump or float around your shoulders. A clogged filter makes the pump work harder, slows heating and on many tubs trips an error code. Cleaning it takes five minutes.
What kind of filter does your tub use?
Almost every inflatable, foam and frame tub on our site uses a cartridge filter: a cylinder of pleated fabric around a plastic core. It sits in a holder inside the tub wall or in the pump unit. Some makers add extras:
- The Canadian Spa Co. Grand Rapids lists Microban filters, which the maker treats against bacteria growth.
- The MSpa Tribeca, MSpa Denver and MSpa Aero Plus have a UVC sanitiser, which helps keep the water clear between changes. It does not replace the filter.
- Intex PureSpa tubs such as the Greywood Deluxe 4 have a hard water system, which helps with limescale. It does not replace the filter either.
Check your manual for the exact cartridge your tub takes. Cartridges look alike but do not always fit.
How often to clean it
| Job | How often |
|---|---|
| Quick rinse | Every few days of use, and after a busy session |
| Deep clean | Every few weeks, or when a rinse no longer brings the colour back |
| Replace | When it stays grey after a deep clean, or the pleats tear or go floppy |
Heavy use, lots of bathers and sun cream all shorten these gaps. Tie the deep clean to your water change and you will not forget it.
Quick rinse: step by step
- Switch the tub off at the socket. Never take the filter out while the pump runs.
- Remove the filter. Twist or lift the holder as your manual shows. Some tubs have a cap to unscrew first.
- Take the cartridge out of the holder, if your tub uses one.
- Rinse with the garden hose. Hold it at an angle and work from the top down, spraying between every pleat. Use a normal nozzle, not a jet setting.
- Check the pleats. Gently open them with your fingers and rinse again where you still see dirt.
- Put it back and switch the tub on.
Do not use a pressure washer. It can tear the fabric and push dirt deeper into the pleats.
Deep clean: step by step
A rinse does not shift oils from skin and sun cream. These build up in the fabric and make the filter less effective even when it looks clean.
- Rinse first, as above.
- Soak the cartridge in a hot tub filter cleaner mixed with water in a bucket. Follow the dose and the soaking time on the product.
- Rinse again thoroughly. Any cleaner left in the pleats will foam up in the tub.
- Let it dry fully before you put it back, if you can. Drying helps loosen remaining dirt, which you can then brush off with a soft brush.
The easy way to do this is with a spare cartridge. Put the spare in the tub while the other one soaks and dries. You never have the tub out of action, and you can rotate the two.
Things that damage a filter
- The dishwasher or washing machine. Heat and detergent warp the core and leave soap in the fabric.
- Household bleach or washing up liquid. Both can damage the fabric and cause foam in the water.
- A stiff brush or pressure washer. Both tear the pleats.
- Running the tub without a filter. Grit goes straight into the pump. Some tubs refuse to run without one, others will run and wear out.
When to throw it away
Replace the cartridge when:
- It stays grey or brown after a deep clean
- The pleats are torn, frayed or flattened
- The end caps are cracked
- The water stays cloudy even with balanced chemicals and a cleaned filter
Keep a spare in the shed. Filters are cheap compared with a pump.
Signs your filter needs attention now
- The water looks cloudy or has a film on top
- The tub takes longer than usual to heat
- The bubbles or jets feel weaker
- The pump shows a flow error code
If any of these appear, clean the filter before you reach for more chemicals. Often that is the fix. If it is not, test the water and read our chemicals for beginners guide.
Quick answers
Can I clean the filter with just water? For routine rinses, yes. For a deep clean, use a filter cleaner made for hot tubs.
Does a UVC sanitiser mean I clean the filter less? No. UVC treats the water. The filter still catches dirt and needs the same care.
Should I clean the filter when I change the water? Yes, and it is a good time to swap in your spare.
More on keeping the water right: hot tub water care and winter use, how long inflatable hot tubs last and hot tub energy saving tips.
